// wscompand.c
// waveshaping compander, mostly for speech
/*
This file is part of a program that implements a Software-Defined Radio.

Copyright (C) 2004, 2005, 2006 by Frank Brickle, AB2KT and Bob McGwier, N4HY

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

The authors can be reached by email at

ab2kt@arrl.net
or
rwmcgwier@comcast.net

or by paper mail at

The DTTS Microwave Society
6 Kathleen Place
Bridgewater, NJ 08807
*/

#include <include.h>

PRIVATE INLINE REAL
WSCLookup (WSCompander wsc, REAL x)
{
  if (x > 0.0)
    {
      REAL d = x - (int) x, y, *tbl = wsc->tbl;
      int i = (int) (x * wsc->npts), end = wsc->nend;
      if (i < end)
	y = tbl[i] + d * (tbl[i + 1] - tbl[i]);
      else
	y = tbl[end];
      return y / x;
    }
  else
    return 0.0;
}

void
WSCompand (WSCompander wsc)
{
  int i, n = CXBsize (wsc->buff);

  for (i = 0; i < n; i++)
    {
      COMPLEX val = CXBdata (wsc->buff, i);
      REAL mag = Cmag (val), scl = WSCLookup (wsc, mag);
      CXBdata (wsc->buff, i) = Cscl (val, 0.8f*scl);
    }
}

void
WSCReset (WSCompander wsc, REAL fac)
{
  int i;
  REAL *tbl = wsc->tbl;

  if (fac == 0.0)		// just linear
    for (i = 0; i < wsc->npts; i++)
      tbl[i] = i / (REAL) wsc->nend;

  else
    {				// exponential
      REAL del = fac / wsc->nend, scl = (REAL) (1.0 - exp (fac));
      for (i = 0; i < wsc->npts; i++)
	tbl[i] = (REAL) ((1.0 - exp (i * del)) / scl);
    }
  wsc->fac = fac;
}

// fac < 0: compression
// fac > 0: expansion

WSCompander
newWSCompander (int npts, REAL fac, CXB buff)
{
  WSCompander wsc;

  wsc = (WSCompander) safealloc (1,
				 sizeof (WSCompanderInfo),
				 "WSCompander struct");
  wsc->npts = npts;
  wsc->nend = npts - 1;
  wsc->tbl = newvec_REAL (npts, "WSCompander table");
  wsc->buff = newCXB (CXBsize (buff), CXBbase (buff), "WSCompander buff");
  WSCReset (wsc, fac);
  return wsc;
}

void
delWSCompander (WSCompander wsc)
{
  if (wsc)
    {
      delvec_REAL (wsc->tbl);
      delCXB (wsc->buff);
      safefree ((char *) wsc);
    }
}
